1. Field of the Invention
The present invention relates to a display device provided with a self-emission element, especially to a display device provided with an electroluminescent element and a thin film transistor.
2. Description of the Related Art
In recent years, electroluminescent (hereafter, referred to as an EL) display devices with an EL element have been receiving an attention as a display device substituting for a CRT and an LCD. For example, research and developments are being pursued for the EL display device provided with a thin film transistor (hereafter, referred to as a TFT) as a switching element for driving the EL element.
The above-mentioned EL display device is formed, for example, by laminating the TFT and an organic EL element sequentially on a transparent glass substrate (hereafter, referred to as an insulating substrate).
A gate electrode is formed on the insulating substrate, and a gate insulating film and an active layer made of a p-Si film are laminated sequentially thereon.
In the active layer, a channel is provided above the gate electrode, and source and drain regions are severally provided on both sides of the channel above the gate electrode.
An interlayer insulating film is formed on the whole surfaces of the gate insulating film and the active layer, and a drain electrode is formed by filling metal such as Al in a contact hole provided correspondingly to the drain region.
Furthermore, on the whole surface of the interlayer insulating film, there are formed a planarization insulation layer for planarizing the surface, which is made of, for example, organic resin, and a contact hole on a position corresponding to the source region in the planarization insulation layer. On the planarization insulation layer, there is formed an anode of the EL element, which serves as a source electrode made of ITO (Indium Tin Oxide) and contacting to the source region through the contact hole.
A hole transport layer is formed on the anode of ITO and an emissive layer is formed thereon. An electron transport layer is formed to cover the emissive layer and a cathode is laminated thereon.
FIGS. 7A and 7B are explanatory views of a sealing structure of a conventional EL display device. As shown in FIGS. 7A and 7B, a device substrate 200, which is integrated with the above EL elements, and a sealing substrate 300 made of a glass substrate are attached together with a sealing resin 400 interposed therebetween which is made of, for example, epoxy resin and coated on the sealing substrate 300 by a dispenser. The device substrate 200 and the sealing substrate 300 are attached together by heating and hardening the sealing resin 400 interposed therebetween.
In this adhesion, a desiccant is coated on the sealing substrate to absorb moisture from outside, thereby reducing the effect of the moisture on the operation of the EL element. In doing so, only the weight of the desiccant is considered in terms of the moisture absorption capacity of the desiccant. The conventional device with such a desiccant, however, is not efficient in the moisture absorption.